Laboratory investigations are proposed to define in vitro parameters of cell-mediated immune response to cancer cells enzymatically desialylated with neuraminidase in patients with solid tumors or inbred rats bearing syngeneic tumors. Studies include: (a) fractionation of blood serum from tumor-bearing hosts to prepare serum sialoglycoproteins with non-specific serum immunosuppressive activity; (b) definition of the mode of action of such immunosuppressive sialoglycoproteins; (c) definition of the anatomic site of origin of such substances; (d) study of asialyl-mediated immunogenic augmentation methods in producing inhibition of growth of established syngeneic tumors; and (e) study of immunosuppressive action of such serum glycoproteins in in vitro allogeneic reactions or lectin stimulation cultures.